Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2016		Apr. 30, 2015		Apr. 30, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 10		$ 9		$ 9
Additions Charged to Costs and Expenses	1		2		0
Additions Charged to Other Accounts	0		0		0
Deductions	2	[1]	1	[1]	0
Balance at End of Period	$ 9		$ 10		$ 9

[1] Doubtful accounts written off, net of recoveries.